The present invention relates to a chassis structure for a motor vehicle.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Constructional, technological and material lightweight solutions for weight reduction of chassis structures for motor vehicles gain increasingly importance with respect to reduction in fuel consumption and emission. Lightweight materials such as aluminum play a special role to reduce the so-called unsprung masses in the chassis area. This trend is further accelerated by the fact that low-emission or emission-free vehicles with hybrid or electric drive require added weight of about 130 kg to account for the required electric components. This weight has to be compensated through greater weight reduction of other components. To ensure the required high strength and stiffness properties of chassis structures, like pivot bearing, support arm, guide arm, A-arm etc., which are subject to high stress while still having a smallest possible own weight, chassis structures forged from aluminum with yield strength Rp0.2 of above 300 MPa and elongation at rupture A5 of above 10% are increasingly in demand. In addition to the yield strength as dimension criterion, chassis structures are also dimensioned for stiffness to withstand defined buckling loads in particular stress and crash situations. Crucial for the stiffness is the modulus of elasticity of the used material in addition to the cross section configuration. The modulus of elasticity of aluminum is about 70,000 kN/mm2 which is three times smaller than that of steel. As a result, component regions that are critical with respect to stiffness encounter the undesired situation that the solid cross sections common in forged parts have to be increased to satisfy the demanded stiffness, causing additional mass and thus increased weight. As vehicles are built increasingly more compact also in the area of the chassis, space restrictions prohibit however a random increase of component cross sections in order to realize the required values for the stiffness-relevant section modulus of the component cross section, e.g. through use of lightweight hollow sections of greater diameter instead of massive cross sections.
As the stiffness-relevant modulus of elasticity of lightweight materials, like aluminum or other materials, can be influenced within very narrow limits only, known solutions propose the use of composites with materials of higher modulus of elasticity. For example, it is known to forge steel structures of varying geometric shape and thickness with a modulus of elasticity of about 210,000 kN/mm2 onto stiffness-relevant regions of forged aluminum parts. Galvanic susceptibility to corrosion between galvanically relevant contact zones between aluminum base material and steel structure as well as corrosion of the steel surface itself has however been proven problematic. This is especially true when considering that such forged aluminum parts cannot be provided with an additional corrosion protection layer for cost reasons.
The use of various types of composites, e.g. composite of layers, particle composites, fiber composites etc., in shipbuilding, aircraft construction etc., have also been known which involve a layering of varying materials. These technologies are however unsuitable for cost reasons. A further known approach involves the use of metal matrix composites (MMC) which achieve a greater modulus of elasticity through incorporation of ceramic fibers in the aluminum matrix. High production costs for these metal matrix composites limit this technology to special applications and uses however. In particular known from Formula 1 motor racing are CFRP-based complete solutions which however are unsuitable for application in conventional automobile industry in view of their high costs and relatively brittle and deformation-resistant fracture behavior.
It would therefore be desirable and advantageous to provide an improved chassis structure to obviate prior art shortcomings.